A number of methods exist for focusing an IR camera. Focusing may be performed manually by adjusting the optics by hand. It may also be performed by automatic means by means of a focus motor based on some indication of object distance.
It is becoming more and more common that IR cameras, in addition to the IR imaging subsystem, also comprise a visual imaging subsystem. The provision of both an IR imaging subsystem and a visual imaging subsystem, among other things, allows for more sophisticated presentation of image data, in particular fused images, which means that part of the image is shown as IR data and the rest as visual image data. Various types of picture-in-picture techniques exist for creating fused images. Blending is another form of fusion and refers to presenting a value for each pixel based on both the IR data and the visual image data for that pixel.
Co-pending U.S. patent application Ser. No. 11/773,982 discloses a method of focusing an IR camera part in a camera also having a visual imaging part, based on the focus distance determined on the basis of the parallax between the IR image and the visual image.
None of the known methods for focusing an IR camera enables a continuous adjustment of the focus. The focusing function is becoming more and more important because many other features, such as temperature measurements, fusion alignment and image quality, depend on having correct focus.